In the field of magnetic storage systems, an electrical circuit called a read channel transforms physical magnetic flux changes measured in a data read head into abstract bits representing information stored to a magnetic medium. The abstract bits are produced by a symbol or sequence detector, which is designed to achieve a low bit-error rate when reading data written on magnetic media in hard disk drives, tape drives, etc. As the density of data written on the media increases, along with faster write speeds, conventional read-detect methods and devices which read the data stored on the magnetic media often are not adequate to detect the data at the error rates required by the users of such methods and devices.
To address these issues, attempts have been made at improving the performance of data detectors in read channels for magnetic storage systems, in particular tape storage systems. Known solutions to improve the performance of data detectors in read channels that go beyond a standard detector design, such as partial response maximum likelihood (PRML) detection, noise-predictive maximum-likelihood (NPML) detection, data-dependent NPML (DD-NPML), post-processing techniques, and other methods. However, even these methods and devices do not effectively compensate for all of the slight variations in the data being read. For example, non-linear effects, e.g., non-linear transition shifts (NLTS) in the magnetic medium recording and readback processes, may degrade detection performance as the noise becomes non-zero-mean and non-Gaussian, which is not accounted for in NPML or DD-NPML detection.